西双版纳热带季节雨林4种树种幼苗生长死亡对海拔变化的反应

Responses of Growth and Mortality of Seedlings of Four Tree Species of Tropical Seasonal Rain Forest to Increasing Altitude in Xishuangbanna, China

在西双版纳山地选取3个海拔梯度,对热带季节雨林4种主要树种进行幼苗移栽试验,观测幼树生长、死亡沿海拔梯度的变化,目的在于明确海拔变化对热带季节雨林主要树种幼苗生长、死亡的影响,热带季节雨林主要树种幼苗的生长是否在低海拔地区优于在高海拔地区。结果表明,4种幼苗对海拔变化的反应并不相同。绒毛番龙眼和云南玉蕊幼苗的生长和存活主要是受到温度的限制,随海拔的变化表现出显著的差异,这两种幼苗在低海拔上的生长显著优于在中、高海拔上,而云南肉豆蔻和小叶红光树没有表现出在低海拔上优于中、高海拔的特征,这可能是由于它们不适应强光照的生活环境而造成的。

The transplant experiment of seedlings of 4 dominant tree species, Pometia tomentosa, Barringtonia macrostachya, Myristica yunnanensis and Knema globularia, coming from tropical seasonal rain forest, were made on three altitude sites （Menglun 600 m; Caiyanghe 1100 m; Mengsong 1600 m; ） in Xishuangbanna. The objective of this study was to determine how the growth and mortality of seedlings of dominant tree species of tropical rain forest were affected by changed altitude, and whether the seedlings could grow better on low altitude sites than on higher altitude sites. The result of this study is important for forecasting response of tropical forest to the world change. The transplant experiment was performed during the period from September 2003 to September 2004. The number of seedlings of each species on each site is no less than 20. The height and SBD （seedling base diameter） of seedling was measured one time at the end of every month, at one time, the number of mortality, leaves, flushing leaves and defoliation of seedling were recorded on each measurement occasion; the soil water content was determined at interval of half month; the soil nutrient content was measured one time in the period of experiment; the data of temperature and precipitation on three sites were provided by the weather station we set up on the three altitude gradient in 2003. The result shows that with enhance of altitude, whole year precipitation increases and year mean temperature decreases, and soil water content increases along the altitudinal gradient; soil nutrient content on low altitude sites is no better than that on middle and high altitude sites; the height and SBD for P, tomentosa and B. macrostachya decline respectively significantly with the increasing elevation, but M. yunnanensis and K. globularia didn＇t exhibit similar character; the mortality of seedling for the foregoing two species is highest on high altitude site, and for latter two species on middle altitude site; the number of leaves/seedling for all species decrease with increasing elevation; flushing leaf of seedling is more in number or earlier on low altitude site than on middle and high altitude sites; the defoliation occur mainly in dry - season and rainy - season on low altitude site, and in fog- cool season on middle and high altitude sites. We conclude that the respective response of 4 species to changing altitude is different. The growth and survival for P. tomentosa and B. macrostachya were limited by temperature, and the difference is significant among three altitude sites. Seedlings of the two species grow better markedly on low altitude site than on middle and high altitude sites, moreover, M. yunnanensis and K. globularia did not exhibit similar character, which is the result of the maladjustment of the two species to strong light.